The present invention relates to a high-frequency module for configuring a micro communication functional module having an information communication function and a storage function, which is associated with various electronic equipments such as a personal computer, a portable telephone, audio equipment, etc.
Recently, as the digitization of data has been promoted, various types of information such as music information, audio information, and video information can be easily utilized by using a personal computer and a mobile computer. Under the bandwidth compression using the audio codec technique and the video codec technique, such information is easily and efficiently distributed to various communication terminal equipments by digital broadcasting. For example, audio and video data (AV data) can be received by an outdoor portable telephone.
The data transmission and reception systems have been put to practical use widely even in a small-sized area such as a household since desirable network systems have been suggested. As the network systems, there are proposed various wireless communication systems for the next generation such as a narrow band radio communication system of 5 GHz shown in the IEEE 802.11a, a radio LAN system of 2.45 GHz shown in the IEEE 802.11b, and a short-range radio communication system called Bluetooth.
In the data transmission and reception systems, by effectively utilizing such wireless network systems, various data can be transmitted and received easily at various places such as households and outdoors without using a repeater or a repeater station. Also, it becomes possible to have an access to the internet to transmit and receive various data.
On the other hand, in the data transmission an reception systems, small-sized portable communication terminal equipments having an above-described communication function have to be inevitably realized. In communication terminal equipment, a transmission and reception unit is required to perform modulation and demodulation processing for analog high-frequency signals. Thus, in communication terminal equipment, a high-frequency transmission and reception circuit of the superheterodyne system for converting transmission and reception signals to intermediate frequency signals is generally arranged.
The high-frequency transmission and reception circuit has an antenna unit for transmitting and receiving information signals which has an antenna and a changeover switch, and a transmission/reception switching unit for performing switching operation between transmission operation and reception operation. Also, the high-frequency transmission and reception circuit has a reception circuit which consists of a frequency conversion circuit, a demodulation circuit, etc. Moreover, the high-frequency transmission and reception circuit has a transmission circuit which consists of a power amplifier, a chive amplifier, a modulation circuit, etc. Furthermore, the high-frequency transmission and reception circuit has a reference frequency generation circuit for providing the reception unit and the transmission unit with a reference frequency.
The configured high-frequency transmission and reception circuit has large-sized functional elements such as various filters inserted between respective stages, a voltage-controlled oscillator (VCO), an SAW filter, etc., and a great number of passive elements such as inductors, resistors, capacitors, etc. which are particular to a high-frequency analog circuit such as a matching circuit or a bias circuit. Respective circuits in the high-frequency transmission and reception circuit are configured in the form of ICs. However, filters inserted between respective stages cannot be arranged in ICs, and therefor a matching circuit has to be arranged at outside of ICs. So, the high-frequency transmission and reception circuit is large in size as a whole, which obstacles miniaturization and decreasing in weight of a communication terminal equipment.
On the other hand, in a communication terminal equipment, a high-frequency transmission and reception circuit of the direct conversion system which does not convert transmission and reception signals to intermediate frequency signals is also used. In such a high-frequency transmission and reception circuit, information signals received by an antenna unit are sent to a demodulation circuit via a transmission/reception switching unit to be baseband-processed directly. Also, in the high-frequency transmission and reception circuit, information signals generated by a source unit are directly modulated to signals of a predetermined frequency band by a modulation unit without converting the transmission signals to intermediate frequency signals, and thus modulated signals are transmitted from the antenna unit via an amplifier and the transmission/reception switching unit.
In the configured high-frequency transmission and reception circuit, information signals can be received by performing direct detection without converting reception signals into intermediate frequency signals. As the number of parts or elements such as filters can be reduced, the high-frequency transmission and reception circuit can have its entire configuration simplified, and can be substantially configured in the form of one chip. Even in the high-frequency transmission and reception circuit of the direct conversion system, filters and a matching circuit arranged at downstream stages have to be taken into consideration. Also, since amplification processing is performed only one time in a high-frequency stage of the high-frequency transmission and reception circuit, it becomes difficult to obtain enough gain, and amplification processing has to be performed also in a baseband unit. Thus, the high-frequency transmission and reception circuit requires a cancellation circuit of DC offset and an extra low pass filter, which undesirably increases entire power consumption.
As has been described above, in the conventional high-frequency transmission and reception circuit of both the superheterodyne system and the direct conversion system, satisfactory characteristics fulfilling a required specification of miniaturization and decreasing decrease in weight of a communication terminal equipment cannot be obtained. Thus, it is proposed that the high-frequency transmission and reception circuit be configured in the form of a simplified small-sized module using a Si-CMOS circuit as a base. That is, for example, there is proposed a one-chip high-frequency module in which passive elements of high characteristics are arranged on an Si substrate, filters and a resonator are built in a LSI, and a logic LSI of a baseband unit is integrated.
In the high-frequency module, when inductors are arranged on an Si substrate, the Si substrate is provided with holes directly under the inductors, or space is prepared between the inductors and the Si substrate in order to improve the characteristics of the inductors, which undesirably increases the manufacturing cost.
In case the front end of a high-frequency signal circuit is formed on a semiconductor substrate made of Si, SiGe, etc. or on a glass substrate, in addition to a high-frequency signal circuit pattern, a power supply pattern, a ground pattern, and a signal wiring pattern for performing control processing are required to be formed as pattern wiring layers. As multiple pattern wiring layers are formed, there arises a problem of mutual interference between pattern wiring layers, and also the manufacturing cost is undesirably increased.
In case the entire high-frequency module is packaged, the high-frequency module is mounted to an interposer (intermediate substrate) by undergoing wire bonding. However, undesirably, the area for mounting the high-frequency module is caused to be large and the entire thickness is caused to be increased, and also the manufacturing cost is undesirably increased.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a high-frequency module which is small in size and inexpensive, and can improve the characteristics of inductors.
The above object can be attained by providing a high-frequency module, including:
a base substrate which has multiple pattern wiring layers and dielectric insulating layers formed therein, and has a buildup surface for smoothing the upper layer thereof; and
a high-frequency element layer formed on the buildup surface, which has an inductor formed therein via an insulating layer formed on the buildup surface;
wherein the base substrate is provided with a region where the pattern wiring layers are not formed from the upper layer to at least the mid portion thereof along the thickness direction, and the inductor of the high-frequency element layer is formed directly above the region.
According to the high-frequency module employing the present invention, since the inductors are formed directly above the regions where the pattern wiring layers of the base substrate are not formed, the coupling capacitance between the inductors and the pattern wiring layers can be reduced, and high Q value of the inductors can be obtained.